Hlf 2026 Sunday session ‘Scars: Totems of Memory’ explores the molecular, immunological, and psychological dimensions of how our bodies record trauma, Naresh Nunna of Neo Science Hub, reports.
At 11:00 AM on Sunday, the Science and the City stream turned to one of biology’s most visible paradoxes: scars. These marks on our skin, our eyes, our organs are simultaneously protective mechanisms and permanent records of past trauma. “Scars: Totems of Memory,” moderated by science writer Rohini Subrahmanyam, brought together Dr. Sayan Basu from L.V. Prasad Eye Institute and Dr. Sveta Chakrabarti from Manipal Institute of Regenerative Medicine to explore how bodies encode, transmit, and remember damage across cellular, immunological, and tissue scales.
What emerged was a profound meditation on memory itself—not just neurological memory stored in brains, but molecular memory encoded in DNA folding, immunological memory carried by blood cells, and structural memory preserved in scar tissue. The session asked: Why do our bodies choose quick repair over perfect regeneration? What happens when that choice becomes pathological? And in a future where we might control scarring at the molecular level, what would we choose to remember—and what to forget?
Survival Over Function: The Evolutionary Logic of Scarring
Basu opened with the fundamental question: why do we scar at all? “From an evolutionary point of view, we prioritize survival over function. Whenever there is trauma or wounding, the body tries to heal as quickly as possible, which helps us survive the trauma. And restoration of function is like a secondary thing that happens slowly over time.”
He illustrated with Deadpool, the regenerating comic book character. “If you have seen the movie which correctly portrays how it would happen if you actually were able to do it, he has to spend days or weeks when his limbs are growing back. And he is very vulnerable during that period.”
In evolutionary terms, that vulnerability is fatal. “If we were to regrow instead of repair… it would take a lot of time. It would make us very vulnerable… and therefore less able to survive.”
Scarring is the body’s triage decision: stop the bleeding, close the wound, survive today—worry about optimal function later. “Function is kind of something that is lower down on the priority list, especially for eyes. Because we have two eyes and because mostly people get injured in one, so you can still function with the other while the eye that you are injured in repairs and scars.”
The scar also remodels over time. “Over several weeks, several months, in many cases over several years, the scars do get better and less apparent… in the eye you can see better because they become clearer over time.”
When Transparency Turns Opaque: Corneal Scarring
Basu’s clinical work focuses on one of the body’s few completely transparent tissues: the cornea. “When you look at somebody and you look at their eye color, the reason that you can see the color is actually the color inside of the eye, it’s not of the cornea. The cornea is transparent.”
This transparency is optically essential but biologically fragile. “The problem with scarring in the cornea which happens when you get injured or there’s an infection, is that unlike in the skin where… you just leave behind at the most a cosmetic deficit… in the eye when it happens the scar causes an opacity so it leaves a whitish mark which interferes with vision.”
The severity depends on multiple factors: “How bad the injury was, how long it took for the wound to heal… whether it was infected while it was healing or not. That basically influences how bad the scar will be—how big the scar is or how deep the scar is.”
Younger patients heal better. “In smaller children, younger people… when they get an infection, they get a scar, you see them after a few months or a year, you can hardly make out that they had it.” But older individuals or those with other health problems may retain permanent opacities that compromise vision.
Wounding a Fruit Fly: The Challenge of Microscale Injury
The moderator turned to Chakrabarti with evident curiosity: “How does the wound healing process in fruit flies work? How do you even inflict a wound in a fruit fly without killing it?”
Chakrabarti’s answer revealed the precision required: “We manipulate the flies under a microscope, so we can actually be able to see it very well, because with the naked eye they are too small.”
Her lab uses “a very thin tungsten needle which we sterilize and then we injure basically under the wing of the fly because that’s very robust tissue. It’s the flight muscle… So even if we go superficially with a needle, the fly is able to clot and heal itself and then able to function properly.”
Other labs use even more precise tools: “You can get as precise as one or two cells by using lasers… with a very powerful laser just create a very precise wound.”
The admission: “I think we’ve lost a lot of lives to inexperienced undergrad students.”
Blood Cells as Messengers: Inter-Organ Communication After Wounding
Chakrabarti’s research has revealed something unexpected: wounding isn’t a local event. “When we think of wounding we really think about the specific place that you wound… but what we find in our research is as an organism we are not like a closed system.”
Blood cells do more than clean up debris at wound sites. “In the remodeling as well as the proliferation phase, these blood cells are important to tell the other cell types, okay now is the correct time for you to start dividing, lay the scaffold, what do you do at what time.”
Even more remarkably: “These blood cells can actually move to different sites of the body and tell even very distant sites that there has been an injury and some sort of a change has to happen at the organ function.”
When this communication is blocked genetically, consequences emerge later. “If we go and infect the fly with a very benign bacteria which normally it eats in the food, other organs are not functioning properly. So this communication is… very important to know there has been an injury somewhere and how other organs need to change accordingly.”
The Gut Connection: Why the Intestine Responds to Muscle Wounds
The most surprising finding involves the gut. In humans, approximately 70% of immune cells constantly sample the intestinal lining—it’s the organ in most contact with the immune system. In flies without specialized immune organs like spleens, blood cells migrate to the gut after muscle wounds.
“Days later, they’re going and sticking on to the gut of the flies. What are they doing there?” Chakrabarti asked rhetorically. “If we can block that, over the lifespan of the fly, the gut starts to become leaky, there is change in the microbiota. So the functioning of the gut gets impacted over time.”
This makes evolutionary sense. Fruit flies “eat continuously rotting fruits, vegetables… always in contact with any pathogen… fungi, bacteria, it’s a plethora of microbes there. So it needs to heighten up its other organ, which could get contaminated.”
The finding has human parallels. “Patients of atopic dermatitis who are scratching a lot, there are changes seen in their gut as well. They become more susceptible to oral allergens which normally they wouldn’t be.”
Immune Memory: From Vaccination to Epigenetics
Both speakers explored how immune systems remember past traumas. Basu noted that “the immune system definitely has memory… just like we remember past trauma, the immune system also remembers what hurt or caused infection.”
This has profound clinical implications for transplantation. “If somebody has had a transplant, the body remembers the transplant and especially if it has failed. So somebody who has a failure of organ transplantation has a higher chance that the next transplant will fail because the body remembers that this happened.”
Chakrabarti’s work challenges conventional immunology. Standard theory holds that only adaptive immune cells—T-cells and B-cells—maintain memory. But fruit flies lack these entirely. “They don’t have any antibodies, they don’t have any adaptive system at all… How are they able to survive in so many different environments?”
Her experiments reveal memory in supposedly “primitive” innate immune cells. “If I wound a fly and then a few days later, I come in with something very pathogenic, that fly that was wounded survives better. It’s able to deal with a deadly pathogen, which normally a naive fly wouldn’t be able to.”
The mechanism involves epigenetics—DNA folding that doesn’t change genetic sequence but alters gene expression. “Because they’ve had an injury, their DNA is opened up. Next time a pathogen comes, they produce all the peptides that would be needed to kill the microbes.”
Allergy as Dysfunctional Memory
Basu offered allergy as an example of immune memory gone wrong. “The body is able to triage what is innocuous and what is dangerous… over a period of time we are exposed to so many things in the environment… the body responds or adapts.”
Newborns demonstrate this learning process dramatically. “The first time a newborn gets a mosquito bite, they get a really bad reaction to it. But then over a period of time, that reaction becomes milder and milder.”
Allergy represents failure to develop appropriate tolerance. “You are not able to differentiate between what is harmful and what is innocuous. And then you take a longer time to develop this tolerance or this memory—this is not bad, I don’t need to react.”
The Microbiome Factor: More Bacterial Than Human
Basu noted that “all of us carry more bacterial DNA than human DNA with us every day. And most of this bacteria are in our gut and skin, which are the two largest organs, or at least organisms with the largest amount of surface area.”
This enormous microbial community profoundly influences health. Recent microbiome research has revealed resident bacteria even in previously assumed sterile environments. “There’s now some evidence to say even areas we thought were completely sterile… inside the eye, there are resident microbiota.”
Diet influences microbiome composition, which influences disease susceptibility. “If somebody has a certain type of diet, they have a certain type of microbiome and they tend to have less metabolic diseases… the Mediterranean diet.”
The connection extends to wound healing. “If you are diabetic, your wounds heal slower… The longer you have been a diabetic or the worse your diabetic control is, your wound healing is worse.” Before surgery, “blood sugar has to be controlled, because if your blood sugar is high… even if you inflict a surgical trauma, which is a very controlled wound, it might not heal properly, it might get infected.”
Fetal Healing: Life Without Scars
The moderator asked about fetal wound healing, which occurs without scarring. Basu explained the immunological basis: “As the baby is growing in the mother, he doesn’t have an immune signature. So the mother… does not identify the baby as foreign, as another individual.”
The fetus lacks a developed immune system. “It does not even have an evolved or developed immune system. So it can’t scar. Neither can it scar by itself, nor can the mother inflict a scar on the baby while it is in womb.”
Chakrabarti added that the fetal environment itself matters. “If we think of why a scar has to be there, basically it’s a physical plaque so that from the external environment you don’t get something entering in which would harm your body. So if we think of a fetus, it’s already in a very protected environment away from all the pathogens.”
Fetal tissues themselves become therapeutic tools. “Amniotic membrane… is used routinely clinically for wound repair, even in the eye. Particularly patients with burns… who have very bad injury… we use part of the amniotic membrane to cover that and that is known to have special wound healing properties.”
The Future: Choosing What to Remember
As the session drew to close, the moderator posed a philosophical question: In a future where molecular control allows scarless healing, what should we choose to remember?
Basu emphasized that complete elimination of scarring would be dangerous. “You don’t want to get rid of the body’s ability to scar… because that would be harmful. But you may want to control how badly it scars or how severely it scars.”
The current increase in adult-onset allergies stems partly from insufficient childhood exposure. “Kids are not exposed enough and they tend to develop allergies more because they are not going through this process of developing tolerance.”
Chakrabarti agreed: “The function of the tissue is really important… The reason we scar is to keep us safe and survive.” As environments become cleaner, “those threats are getting away from us… maybe in a foreseeable future we could choose if we wanted to keep some scars versus others.”
But she cautioned: “When we are not exposing the immune response to these kind of challenges, maybe there might be other problems that might happen… Maybe this effect of the scar might in fact educate your immune system for the future.”
Basu concluded: “The process has to be in place. You have to allow the body to develop the mechanism to react… because it might be critical for your survival if you are able to scar. So you don’t want to get rid of the body’s ability to do that but when you are scarring you want to modulate that process just enough to have the right balance that you don’t scar too much.”
Memory Across Scales
What made this session remarkable was its movement across biological scales—from epigenetic DNA folding in immune cells to blood cell migration between organs to tissue remodeling over months and years. Each scale revealed a different form of memory: molecular, cellular, structural.
The title “Scars: Totems of Memory” proved apt. These marks are indeed totems—physical embodiments of past events that continue to influence present function. They record not just what happened but how the body chose to survive it, prioritizing speed over perfection, closure over restoration.
In exploring regenerative medicine’s promise to flip the switch from repair to regeneration, both speakers acknowledged a paradox: the very mechanisms that leave us scarred also keep us alive. Perfect healing might be possible, but would it be adaptive? Some memories—painful as they are—serve purposes we don’t fully understand.
